This invention relates to a fuel injection equipment for an internal combustion engine.
In Japanese Patent Application Laid-Open Publication No. 122733/1984 (59-122733) which discloses a conventional fuel injection equipment for an internal combustion engine, it is proposed to provide the fuel injection equipment with an electronic control system for permitting a fuel pressure applied to an injection nozzle for injecting fuel into an inlet pipe of an internal combustion engine to be controlled in proportion to an engine rotation speed by means of a control unit. More specifically, the control unit carries out an operation for increasing the fuel pressure in proportion to the engine rotation speed. An output of the control unit is input to a pump driving circuit, so that the pump driving circuit varies a delivery pressure of depending upon the output of the control unit, to thereby vary the fuel pressure. The actual fuel pressure is detected by a fuel pressure sensor, of which a detection signal is feed-backed to the control unit, to thereby control the fuel pressure.
Also, Japanese Patent Application Laid-Open Publication No. 122734/1984 (59-122734) proposes to provide a fuel injection equipment with an electronic control system for permitting a fuel pressure applied to an injection nozzle of a fuel injector to be controlled in proportion to an engine rotation speed by means of a control unit. In the fuel injection equipment disclosed in the publication, the fuel pressure is controlled by controlling an electronic control valve arranged in a fuel counterflow passage returned from a fuel pump to a fuel tank depending upon an output of the control unit while keeping a delivery pressure of the fuel pump.
In each of the conventional fuel injection equipments described above, a dynamic range of the fuel injector is apparently reduced to decrease an injection time lag of the fuel injector when an engine rotation speed is kept high. This permits the fuel injection equipment to readily accomplish an increase in the amount of fuel which is required at a high engine speed as well.
As described above, the prior art is so constructed that the fuel pressure is electronically controlled by means of the control unit. Unfortunately, such construction causes a complicated control means to be required for controlling the fuel pressure. Also, the electronic control by means of the control unit requires a stable power supply, so that it is required to use a battery as a control power supply. Thus, the conventional fuel injection equipment fails to be used for an internal combustion engine which does not use a battery as a control power supply.